The present invention introduces a new category of motorized personal water craft: a high speed, high thrust, high performance craft with no steering mechanism for turning. The present invention is a stable, maneuverable, high speed motorized water ski suitable for use by a single rider standing on a rear deck. The rider may turn the water craft according to the present invention solely through his body position, stance and weight distribution. Exceptional speed, maneuverability and rider/craft stability are achieved by a unique and precisely calculated combination of several design parameters including, thrust, speed, weight, engine power, buoyancy, placement of mechanical components to provide a precisely located center of gravity, bottom hull/rail configuration and hull structure.
Prior art motorized personal water craft include: (a) high powered, high speed craft with swivel jet steering mechanisms (devices) for turning; (b) low speed, low performance craft with rudders and other steering mechanisms for turning; and (c) low speed, low performance craft with no steering mechanism for turning.
Many high powered motorized personal water craft that have previously been available use movable jet nozzles or other mechanisms for turning the craft. Such water craft may support either a seated or standing rider. The engine position and cockpit structure of previous motorized aquatic vehicles cause the net center of gravity of the craft plus rider to be substantially in front of the rider while making a turn. All steering devices such as directional nozzles and rudders cause the pivot point to be far in front of the rider, which causes instability. This location of the net center of gravity causes the pivot point for making turns to also be substantially in front of the rider. The forward net center of gravity renders these craft unsuitable for high speed or high performance use by a standing rear mounted rider. In particular, the forward center of gravity causes rider instability. With such craft it is impossible to make high speed turns solely under the control of the rider's stance and weight distribution.
In addition to the very high and forward net center of gravity and extreme forward pivot point of heretofore available stand-up and sit-down high powered personal water craft, these craft also have high, slightly curved, vertical side rails. Consequently, if the rider leans to the side without using a directional nozzle to turn the craft in a direction opposite to the direction he is leaning, the rider typically loses his balance and takes an unexpected plunge into the water.
The inertia of the rider's body causes the rider to tend to travel in a straight line. As the prior art craft starts to turn, the rider feels it move laterally under him as he continues to tend to move in a straight line. Therefore, in executing turns with such personal water craft, the standing rider's body moves from side to side relative to the craft. Sudden turns can cause the rider to lose his sense of balance.
A movable pump nozzle is used to turn one type of prior art jet-driven standup water craft (commonly referred to as a Jet Ski). The nozzle is directed away from the longitudinal axis in a plane generally parallel to the water. The nozzle then causes a torque or moment about a vertical axis through the net center of gravity of the craft and rider. In operation, if water is propelled to port, the stern of the craft rotates to starboard while the bow turns to port. This movement of the bow and stern is due to the fact that the craft will pivot about its net center of gravity, which is located far forward of the rider.
Therefore, when the rear mounted rider of this type of personal water craft turns the pump nozzle, the craft rotates about the forward center of gravity. The rider's body moves from side to side, which causes a sensory loss of balance or stability. This is a serious stability problem that is addressed by the prior art by increasing the size and weight of the craft in order to achieve acceptable stability for the rider. This also is the reason for the popularity of sit-down craft, which typically use a directional nozzle for turning. The directional nozzle turns left or right and causes the tail to slide in the opposite direction. Because the rider is sitting, he is better able to accommodate instability during turns.
It also must be appreciated that in today's market, a personal water craft is expected to attain speeds of between 30 and 55 miles per hour (approximately 50 to 88 km/hr). A desirable feature of high performance personal water craft is the capability of turning and maneuvering the craft solely by movement of the rider's body. Currently available high speed personal motorized water craft do not provide the capability of being controlled by rider stance and weight distribution. Rather, the body movement associated with the rider of the present day water craft is only in reaction to the directional thrust of a water jet or other turning mechanism in order to maintain stability to prevent the rear mounted rider from being thrown from the craft during maneuvers.
Previous attempts to provide a motorized personal water craft for a standing rider using mechanisms other than swivel jets for turning have been necessarily low speed, low thrust, low performance craft. Some such craft use rudders for steering. These craft do not utilize the relationship of the location of the rider to the location of the center of gravity for negotiating stable turns.
U.S. Pat. No. 3,548,778 to Von Smagala-Romanov discloses a self-propelled surfboard having a propeller that is driven by an internal combustion engine. The propeller is located in a recess in the bottom of the board. The propeller blade is housed within a shield to prevent the blade from contacting a swimmer or the rider if he should fall off the board. The internal combustion engine is mounted within a cavity located centrally of the front and rear ends of the board. The driving propeller is mounted closely behind the engine so as to be generally under the deck portion where a rider would stand.
Von Smagala-Romanov discloses a low power, low speed craft that cannot be made to turn without the use of a rudder, movable jet or other mechanical steering apparatus. Von Smagala-Romanov discloses that his device could be made steerable by incorporating an optional mechanized fin using appropriate cables controlled by rider. By indicating that the craft can be made steerable by using a rudder, movable jet, mechanized fin or other mechanical steering apparatus; Von Smagala-Romanov shows that he did not consider the location of the center of gravity as being a factor in turning. It is evident from the disclosure of Von Smagala-Romanov that the location of the net center of gravity of the craft and rider has nothing to do with the steering or maneuvering of the Von Smagala-Romanov craft. Furthermore, careful study of the Von Smagala-Romanov device indicates that it is a low buoyancy craft that would support only a light-weight rider.
At best, Von Smagala-Romanov is necessarily a low power, low speed craft incapable of a speed anywhere near 30 miles per hour. Careful study of the Von Smagala-Romanov device further indicates that it would accommodate only a small engine of about 4 to 5 HP. The small engine would provide insufficient thrust to produce short radius turns. The hull structure of Von Smagala-Romanov is suitable only for low speeds of less than about 8 miles per hour. Any greater speed would raise a safety issue. The drive mechanism (propeller) in the Von Smagala-Romanov craft is located under the rider, exterior to the hull and forward of the stabilizing fin. This underwater location of the drive mechanism would not be efficient or suitable for placement of a high-thrust jet flow pump.
Von Smagala-Romanov does not take into account the critical placement of mechanical components in relationship to the position of its rider in order to achieve acceptable performance even at low speed. In the position of the rider relative to the position of the lower weight mechanical components shown, the rider's weight would dominate. The bow would be raised significantly out of the water, thus producing unacceptable resistance to forward motion. This type of resistance to forward motion is sometimes referred to as the "ploughing effect." If the rider were to move forward to level the craft, assuming there enough flotation for such movement, he would be inconveniently standing where the vent tube and hand control are located.
French patent 2,617,793 to Trotet discloses a motorized nautical board. Trotet uses a low center of gravity that is below the water line to stabilize the board against overturning. However, like the Von Smagala-Romanov craft, the location of the center of gravity in Trotet has absolutely nothing to do with the turning or maneuvering of the craft. Trotet, like Von Smagala-Romanov, teaches the steering and maneuvering of the craft using a moveable rudder or steering mechanism. In the Trotet craft the net center of gravity is forward of the rider so that during a turn, the stern slides to the left or fight, depending on the direction of the turn, which thereby destabilizes the standing rider.
Trotet, with an 80 cc engine capable of no more than 5 to 8 miles per hour and 50 pounds of thrust, teaches a low speed leisure craft rather than a high speed performance craft. The rider of the low speed board of Trotet would be unstable during takeoff while standing on the rear deck. The Trotet board has insufficient thrust for safely making short radius turns even at low speeds because of its forward pivot point and large vertical profile keel, which causes increased water resistance during turns. Replacing the small engine of Trotet with a larger engine, even if the hull were redesigned to accommodate it, would not enable the Trotet craft to have high speed performance features.
The prior art also discloses motorized water craft with no mechanical turning device. None of these craft are capable of high speed controlled turns or responsive, small radius, low speed turns.
U.S. Pat. No. 3,608,512 to Thompson discloses a boat hull that is provided with its own propulsion unit and that accommodates a standing rider. Thompson discloses a substantially flat-bottomed hull filled with buoyant material and having an upwardly open, longitudinally extending compartment that is open rearwardly at the stern of the hull for accommodating an operator in a standing position. A pair of elongate, longitudinally extending singly formed, narrow fins extend laterally of the compartment. The flat bottom surface merges arcuately into the inner faces of the fins and is preferably provided with elongate, longitudinally extending grooves intermediate the fins. A shrouded propeller, jet orifice, or other suitable arrangement is positioned at the stern directly below the open rear end of the compartment and between the fins. A well in the hull near the bow in front of the compartment serves to receive an internal combustion engine. The large bow mounted engine places the net craft plus rear mounted standing rider such that the pivot point on turns would be far in front of the rider, which destabilizes him as described previously. Therefore, this relatively bulky craft would not be capable of executing responsive, stable high speed turns or safe, short radius low speed turns and maneuvers.
U.S. Pat. No. 3,406,653 to Mela discloses a four foot long, nine pound powered float board which cannot accommodate a standing rider. The engine is relatively openly exposed to water and has no bilge pump. The Mela device is capable speeds of only a few miles per hour. Having no sealed engine housing and no bilge pump renders the disclosed device unsuitable for high performance use. The float board has no rails that would permit it to make high-speed turns.
One particular type of motorized personal water craft is sold under the name Surf Jet. The Surf Jet motorized water craft has a top speed of about 22 miles per hour. The Surf Jet has a rear-mounted engine in a compartment that extends a considerable distance above the water line. The heavy, stern mounted engine causes the stern of this craft to sit very low in the water unless the rider stands a considerable distance in front of the engine. The center of gravity of this craft is located within about 20% of the total craft length measured from the stern. The rider is forced to stand at or forward of the craft midlength in order to balance the heavy stern mounted engine and centrifugal pump and to avoid the large vertical protrusion of the engine housing. Because of this protrusion, which is about 1.5 feet above the deck, the rider is inconveniently forced to mount the craft from the side while in the water. The Surf Jet utilizes a maximum 17 HP vertical mounted engine, vertical drive shaft and an inefficient (relative to an axial flow pump) centrifugal jet pump that produces a maximum thrust of about 130 pounds. It is obvious that the center of gravity was not considered in balancing this craft. Increasing the size of the engine and pump to achieve more thrust and performance would be impractical because this would further deteriorate the balance and stability of the craft. Therefore, the Surf Jet design is essentially a low performance craft because the engine must be small in order to keep the rider from having to stand near the bow of the craft to balance it and keep the bow from being too high above the water line. If the net center of gravity is too close to the stem, then at moderate speeds, the bow begins to lift, which causes instability and the ploughing effect.
For many water sports enthusiasts, personal enjoyment from the operation of a powered water craft will be significantly increased if the rider can, at both low and high speed, turn and control the craft solely by rider stance and weight distribution without the use of active steering mechanisms. Such enjoyment is presently not achieved with motorized water craft as it is at lower speeds with non-motorized craft, such as surfboards and body boards, where personal fulfillment is accomplished through the successful and skillful control of the rider's body for manipulating the board.